Bortezomib Stabilizes and Activates p53 in Proliferative Compartments of both Normal and Tumor Tissues In Vivo

Cancer Research Online First Articles by Yuezhen Xue, Nick Barker, Shawn Hoo.. - 1h ago Preview

 
 
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p53 protein, activated and stabilized by post-translational modifications, performs its major functions by inducing DNA repair, cell cycle arrest, or apoptosis through transcriptional activation. Here we determined the ability of p53 protein stabilized via proteasome inhibition to perform similar functions as p53 induced by stresses such as DNA damage. Treating mice with the proteasome inhibitor bortezomib stabilized p53 in stem/progenitor cells of the intestine and stomach, in other proliferating tissues, and in intestinal tumors. Robust basal p53 mRNA levels were observed in the same compartments where p53 was stabilized. Spatial activation of p53 target genes in response to bortezomib in the small intestine demonstrated that CDKN1A and BAX were upregulated in the proliferative crypts but not in the differentiated villi of the small intestine; PUMA was specifically activated at the crypt base of p53 wild-type mice. Thus, cellular context determines the p53 transcriptional target selection. p53-dependent apoptosis was induced in Lgr5-expressing stem cells of the small intestine and high p53 transcriptional activity and apoptosis was induced in intestinal adenomas and in xenograft tumors. Bortezomib inhibited the growth of intestinal adenomas and xenograft tumors with wild-type p53, indicating the importance of p53 in the response to proteasome inhibitors in tissue homeostasis and in cancer therapy.